The district of Rhondda (pronounced Ron-tha), generally referred to as 'the' Rhondda, consists of two urbanised valleys in Glamorgan, on the south Wales coalfield. The two valleys are the Rhondda Fach, 'Little Rhondda', and Rhondda Fawr, 'Great Rhondda', which meet at the village of Porth, from where the Rhondda River flows on to the town of Pontypridd.
Both valleys, formerly renowned for their natural beauty and wooded hillsides, were built up from the mid nineteenth century to exploit the steam coal measures which lay beneath; the mining villages merged into each other to form two lines of ribbon development several miles in length (an urban form common to most of the mining valleys of south Wales). The Rhondda was known for industrial militancy, and the action by the then Home Secretary Winston Churchill of sending troops to Tonypandy, a mid-Rhondda village, in 1911 to police a miners' strike is recalled in local folklore and labour history alike. Maerdy, in the Rhondda Fach, was known as 'little Moscow' for the influence the Communist Party of Great Britain held in the village, although the Labour Party was paramount in the valleys as a whole. The Rhondda suffered very badly from unemployment as demand for coal fell in the 1920s and the Depression, and the population has fallen from 152,781 in 1911 to 72,443 in 2001 (as an indication of the 'boom town' expansion of the Rhondda, in 1851 the population was just 951). In 1913 the Rhondda had 53 coal mines but the last of these closed in 1990.
The Rhondda was created an urban district in 1894, originally named Ystradafodwg UD but renamed Rhondda UD in 1897; it became a municipal borough in 1955. In 1974 Rhondda District became part of the new county of Mid Glamorgan; this was abolished in 1996 and Rhondda merged with the neighbouring districts of Cynon Valley and Taff-Ely to form the unitary County Borough of Rhondda Cynon Taff.